Tenofovir disoproxil fumarate (TDF, formerly known as bis(POC)-PMPA) is a bis-ester prodrug of the acyclic nucleoside phosphonate tenofovir.
Tenofovir disoproxil fumarate is as an orally-active form of tenofovir. Tenofovir which is chemically named as 9-[2-(R)-(Phosphonomethoxy)propyl]adenine, (PMPA), (I) has a strong activity against human immunodeficiency virus infection in humans.

U.S. Pat. No. 5,733,788 describes a process for the synthesis of PMPA wherein (R)-9-[2-(hydroxyl)propyl]adenine is condensed with diethyl p-toluenesulfonyoxy methylphosphonate in the presence of lithium hydride followed by dealkylation to give tenofovir disoproxil.
U.S. Pat. No. 5,922,695 describes a process for the synthesis of PMPA wherein the condensation is carried out using lithium tert-butoxide. It is further disclosed that tenofovir disoproxil base is obtained as an oil which is converted to its fumarate salt.
Several patents such as US 2004/0018150, U.S. Pat. Nos. 6,465,649, 5,935,946, 5,977,089 disclose various processes for the synthesis of tenofovir disoproxil and its salts. In all of these processes, tenofovir disoproxil base is either described as an oil or is converted to its fumarate salt without isolating the base.
WO 2008/007392 describes tenofovir disoproxil base as a crystalline solid. The crystalline base is characterized by IR, XRD and DSC and is isolated from the reaction mass after being subjected to multiple steps of purification and crystallization. Finally, crystalline tenofovir disoproxil base is isolated from an organic solvent.
Tenofovir disoproxil is a very important candidate for the treatment against HIV virus, as is evident from the literature which describes various attempts to provide alternate methods for the synthesis of this drug for the benefit of society. The present invention is one such attempt in providing a simple and eco-friendly process for the isolation of tenofovir disoproxil base.